1. Field of Invention
The invention relates to an apparatus and a method for controlling lines rendered by a printer or displayed on a monitor that is compatible with antialiasing image data and requires a minimal amount of scanned image data buffering.
2. Description of Related Art
Today""s marking devices typically do not match the idealized printer model used in the construction of images. For example, instead of crisp, square, non-overlapping pixels, as shown in FIG. 1, a real device may draw large, circular spots with gradual boundaries that overlap to fully cover the pixel areas, as shown in FIG. 2.
When lines and characters are drawn using these real spots, they may be thicker or thinner than their intended ideal. The actual behavior of the marker can be complex, for example, making thin lines too thick and thick lines too thin. A rendering process can be employed to adjust the width of lines and characters to compensate for the marker. One approach is to adjust the width of lines when they are rasterized, but is not always effective because the line may not always remain in isolation. For example, one might construct a color sweep by drawing a series of lines of varying color one next to another. Accordingly, adjusting the width of each line in isolation might only serve to destroy the sweep. An alternative approach is to analyze the completely rasterized image to detect lines and to alter their widths. However, to detect and alter lines up to width N pixels in a conventional manner, where the alteration is a function of line width, requires a window of 2N+3 pixels square. Thus, 2N+3 scan lines must be buffered. However, this memory is expensive if the width N is large.
The exemplary embodiments of the invention provide a method and system for compensating for the line width growth or shrinkage in an image rendering system that supports high-addressability. The amount of width adjustment can be a function of the line width. The method is applied after rendering, to the sub-pixel, bit patterns and is compatible with antialiasing and other sub-pixel rendering techniques such as half-bitting. The method and system also require less scan buffering for marker line width compensation than conventional methods. More specifically, the method and system require N+3 scans to detect and adjust widths up to N pixels instead of the 2N+3 necessary conventionally.
This, and other features and advantages of this invention are described in or are apparent from the following detailed description of the system and methods according to this invention.